This invention relates to measurement devices, and more particularly to a system and method for determining the quality and other parameters of fluids.
Transducers for measuring liquid level and other parameters are often used in vehicles, industrial equipment and other systems and components. The electrical output of such transducers change in response to a change in the liquid being measured, and is typically in the form of a change in resistance, capacitance, current flow, magnetic field, frequency, and so on. These types of transducers may include variable capacitors or resistors, optical components, Hall Effect sensors, strain gauges, ultrasonic devices, and so on.
In vehicles, industrial equipment and other systems powered by diesel fuel, a Selective Catalytic Reduction (SCR) system has been used to inject urea—a liquid-reductant agent—through a catalyst into the exhaust stream of a diesel engine. Urea sets off a chemical reaction that converts nitrogen oxides in the exhaust into nitrogen and water, which is then harmlessly expelled through the vehicle tailpipe. Previous urea quality sensor solutions have attempted to address industry quality control by ensuring that a specific quality of urea can be delivered into the exhaust gas stream. If the engine is operated without urea solution in the onboard urea tank, excessive NOx emissions can occur. Using a urea quality sensor, the SCR system can monitor the contents of the urea tank to alert an operator and/or system that the urea tank has been filled with other fluids, e.g., with tap water, coolant, windshield wiper fluid, oil, incorrect concentrations of urea solutions, and so on, instead of the correct concentration of urea solution. The introduction of a urea quality sensor into the SCR system also reduces the risk of tampering or accidental mis-filling and helps ensure compliance to environmental legislation, thus satisfying concerns of users and legislators alike. The urea quality sensor is intended to contribute to the overall success of SCR as a NOx reduction technology. However, prior art solutions for measuring the presence or absence of the required urea concentration, such as refractive index measurements, capacitive, acoustic, and other known techniques, have been unable to measure the urea concentration with any degree of suitable accuracy to meet rigid industry and legislative requirements.
It would therefore be desirous to provide a system and method for determining the quality of fluids and other parameters with a higher degree of accuracy than prior art systems and methods in order to quantify whether or not proper fluid and/or the proper concentrations of fluids are being used in vehicles, machinery, and so on.